1. Field of the Invention
The present invention generally relates to vehicle stabilization equipment such as shock absorbers and, more particularly, to shock ansorber end mounts.
2. Description of the Prior Art
Market demand for stabilizer shock absorbers is high. The reason for the demand is related to large numbers of sport utility vehicles such as vans, pickups, jeeps and the like, which have experienced a great increase in popularity. Today's younger, more affluent generation includes a large number of people who spend their free time driving in backcountry areas and thus require an all-terrain vehicle. Also included are many people who have children and thus require more passenger and cargo room in their vehicles. Over the years, the size of most passenger cars offered for use on our highways has been considerably reduced, with a corresponding decrease in vehicle carrying capacity and power. These conditions have fostered a demand for a new breed of vehicle: the sport utility vehicle, which is generally characterized as powerful and fun to drive, yet also roomy and practical.
A serious shortcoming of sport utility vehicles, however, is their notoriously stiff ride and lack of stability, especially on rough roads, around corners and during hard braking. One solution to the problem has been to install stabilizing equipment such as heavy-duty shock absorbers which can provide sway-free control and a better overall ride.
Basically, a shock absorber includes a piston rod connected to a piston which reciprocates inside a shock absorber barrel filled with a viscous fluid. A shock absorber dampens the oscillations in the spring connecting the vehicle body to an axle and a wheel. By doing so, the associated tire stays in contact with the road and does not bounce excessively. Sport utility vehicles, however, require heavy-duty shock absorbers to compensate for their added weight and harsher operating environments.
One such heavy-duty shock absorber, the overload shock absorber, has historically been the primary weapon used against harsh ride and poor handling, attributes common to most sport utility vehicles. An overload shock absorber is characterized by a spring simply coiled around the outside of a conventional shock absorber. The spring on the overload shock absorber serves to dampen vehicle oscillations on compression.
However, an overload shock absorber is limited by the fact that only piston compression is relieved by the external spring, that is, the force produced when the vehicle "drops" onto the wheels and axle. Piston tension forces are not relieved by the overload shock absorber because the outer spring is retained as a free-floating spring wherein the shock absorber piston rod and mount, and shock absorber barrel, are not attached to the spring. The overload shock absorber is still in use today; however, it is a comparatively inferior design when compared to the stabilizer shock absorber.
The best heavy-duty shock absorber presently available for sport utility vehicles is the stabilizer type shock absorber. A stabilizer shock absorber is a conventional hydraulic shock absorber with a spring coiled around the outside and connected on one end to the shock absorber piston rod, and on the other end to the shock absorber barrel. Unlike the overload shock absorber, the stabilizer shock absorber also dampens shock absorber oscillations under tension. One example of a stabilizer shock absorber is disclosed in U.S. Pat. No. 3,951,391 to Papousek, which document is hereby incorporated herein by reference.
It is the combination of four stabilizer shock absorbers on a vehicle, undergoing opposing tension and compression, that provides stabilization of roll and pitch. For example, when cornering, centrifugal force causes the weight of a vehicle to be thrown to the side of the vehicle closest to the outside of the curve, resulting in the outside of the vehicle "sinking" and the inside of the vehicle "rising". This effect is known as sway, or roll. Unnecessary roll reduces a driver's ability to maneuver a vehicle around a corner. With stabilizer shocks, a vehicle undergoing cornering will level out, since the shocks located on the outside of the vehicle will "push" the chassis up and the inside shocks will "pull" the chassis down.
As another example of vehicle stabilization, pitch, or nosediving, is induced in a vehicle when a vehicle comes to a sudden stop. Stabilizer shocks counteract this natural tendency by pushing up on the front of the vehicle and pulling down on the rear. Stabilizer shocks can push on compression and pull on extension because one end of the spring is held in place against the piston rod and the other end of the spring is affixed to the shock barrel.
Unfortunately, present producers of stabilizer shock absorbers must custom manufacture each shock depending on the type of end mount required by the conveying vehicle. In particular, upper shock absorber end mounts must be welded onto piston rod ends. End mounts are the means by which a shock absorber is connected to a vehicle. Typically an upper end mount connects the shock to a chassis, and a lower end mount connects the shock to an axle or wheel. During stabilizer shock absorber production, for example, a manufacturer will take off-the-shelf hydraulic shock absorbers without end mounts, install an outer spring and spring collars, as described in the Papousek reference, and weld on either an eye ring end mount or a threaded stud end mount as required by the particular vehicle.
Unfortunately, there are three significant manufacturing problems which have heretofore prevented the production of a standardized stabilizer shock absorber for all of the usual applications. First, the length of the piston rod associated with an eye ring end mount is different from the length of the piston rod used with a threaded stud end mount. Therefore, for each size of shock absorber, two styles of shock absorbers having different piston rod lengths must be stocked. Second, the eye ring type of end mounts of current stabilizer shock absorbers require that a second, upper, spring collar be used. This means that eye ring end mounts are inherently more costly to manufacture than stud end mounts due to the additional spring collar. Third, since an upper spring collar is required for eye ring end mounts, but not for stud end mounts which function in conjunction with a pigtail end spring, every class of pressure rated spring such as, for example, springs rated at 100 lbs./sq. in., require one spring with a pigtailed end (for stud end mounts) and one without (for eye ring end mounts).
Consequently, a need exists for an improved stabilizer shock absorber which is standardized and hence readily adaptable to many different applications resulting in an efficient means of manufacture and a reduction in the number of inventoried parts required for their manufacture.